No you misunderstand, Cauliflau wasn't a genuine threat to Beerus. He had simply agreed to a deal that if the Time Patrollers could match him at the level of power he intended to use to destroy Demigra, then he'd give them a crack at the Demon God before he did the deed himself, likely destroying the Time Nest in the process. Everyone gets beaten like a redheaded stepchild, but Caule convinces Beerus to let him and his sister Flau try fusion against him. The result, Cauliflau, puts up a much better fight than anyone else but even as her power skyrockets can't seem to reach even a Beerus that's toying with her. After taking a legendary beating from him, the fusion between Caule and Flau reaches a perfect sync, which manages to trigger Super Saiyan God. They have just enough energy to launch themselves with Beerus with a punch strong enough to bury him in a cliff and seemingly knock him out, then they defuse in a completely exhausted state.
Beerus looks undignified and beaten for a moment, then gets up and dusts himself off like nothing happened. But he's intrigued they managed to reach that height for a moment, so he feigns being sleepy and goes off for a nap, hinting that he won't mind if Demigra is beaten while he's asleep. They don't beat him, they just put him down for a moment while he's holding back.